/* 公共的样式 */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}
html, body {
    font-family:'Gill Sans', 'Gill Sans MT', Calibri, 'Trebuchet MS', sans-serif;
    height: 100%;

    background-image: url(../image/cat.jpg);
    background-repeat: no-repeat;
    background-position: center;
    background-size: cover;/* 将背景图像按比例缩放，确保背景图像在元素内完全可见 */
}
.nav {
    height: 50px;

    background-color: rgb(50, 50, 50);
    color: white;

    line-height: 50px;
    padding-left: 20px;
}
.container {
    width: 100%;
    height: calc(100% - 50px);
    float:left;
    display: flex;
    align-items: center;
    justify-content: center;
}